The use of a control or baseline condition in electrophysiological studies of hemispheric specialization of function

Asymmetries in event-related potential (ERP) measures between the two cerebral hemispheres in humans may not be apparent when the absolute values of left and right hemisphere recordings are only considered within the context of one experimental condition. ERP asymmetries may only emerge when results obtained during experimental conditions designed to differentially activate the two cerebral hemispheres are compared to a baseline or control condition involving low-level cognitive demands. Both theoretical and empirical considerations of such a baseline condition are discussed.